ИСТИНА

The lack of donor organs is a major problem in modern medicine. A promising solution to this problem is the fabrication of human tissues and organs using 3D bioprinting. Most existing biofabrication methods use scaffolds made from biomaterials or nanomaterials. Recently, an innovative method of biofabrication was proposed, in which 3D tissue constructs were fabricated using scaffold-, nozzle- and label-free magnetic levitation assembly in a non-toxic paramagnetic fluid [1]. The biofabrication building blocks are tissue spheroids – tightly packed aggregates of living cells, having a spherical shape with a typical diameter of 0.2 mm. Collected together in a magnetic trap, tissue spheroids are in contact with each other and thus fuse to form a 3D tissue construct. The magnetic levitation makes it possible to fabricate structures of only simple shape, whereas real organs contain blood vessels. Therefore, it is desirable to form tissue constructs with some internal channels. As a first step in solving this problem, this paper presents the method of magneto-acoustic biofabrication. To create the proper trap, we combined magnetic and acoustic fields. The magnetic system was made of two oppositely oriented magnets with an empty space between them. A cylindrical ultrasonic transducer was placed into this space, and a plastic container with tissue spheroids was placed inside the piezoceramic cylinder. The construct was formed in the region, where the gravity was compensated by the magnetophoretic forces in the vertical direction, and due to the magnetic gradient in the horizontal plane the tissue spheroids moved towards each other, levitating above the bottom of the container. The piezoelectric transducer created standing cylindrical ultrasonic waves. The acoustic radiation force [2] acted from the antinode to the node, forming a ring of tissue spheroids. Holding them in such a trap for 18–20 hours led to the merging of spheroids into a solid ring-shaped living construct. A change in the frequency and amplitude of the wave made it possible to manipulate the size and width of the resulting tissue ring. The work was supported by RFBR 18-29-11076.